The first Phase II objective will be to complete the analysis of antisera raised to hybrid HBc immunogens produced and purified at the end of Phase I. These results will impact the use of other surface-exposed P450 regions previously shown to elicit inhibitory antibodies, as well as future use of the hybrid HBc expression/immunization system, successfully developed and applied during Phase I, for the production of inhibitory and/or specific antibodies to various human P450s involved in xenobiotic metabolism. In addition, longer P450 sequences, corresponding to discrete hydrophilic structural elements that encompass putative inhibitory epitopes, will be inserted into HBc and evaluated as immunogens. Such hybrid particles should evoke a region specific, multivalent polyclonal response that, if inhibitory of P450 catalytic activity, can be subsequently parsed by monoclonal antibody production. Also, two novel HBc particles, strategically engineered to enhance chemical reactivity, will be produced and employed for direct coupling of short synthetic P450-specific peptides to enable rapid production of high affinity, specific antibodies for immunoblotting and human liver microsome phenotyping. This approach will simplify the selection of peptide sequences likely to evoke P450-specific antibody responses while retaining the enhanced immunogenicity provided by HBc. In all cases, antisera will be used to assess antibody utility prior to committing resources to monoclonal antibody production.